Electrophotographic photoreceptors of the kind which have an electrophotographic photoreceptive layer containing photoconductive zinc oxide dispersed in a resin binder, and optionally an interlayer, on a conductive support have been predominately employed as a copying material and a lithographic printing material.
The importance of the interlayer in such photoreceptor is described in a large number of literature articles and patents. Specifically, the interlayer has influences on the adhesiveness between a support and a photoreceptive layer, the photoreceptivity, stains in the non-image area, white spots in the image area (which is a phenomenon wherein the toner does not adhere to the image area in spots) and so on. Besides having influences as described above, in order to strongly bond the photoreceptive layer to the support, the interlayer is particularly required when the electrophotographic photoreceptor is employed as a lithographic printing material, because the photoreceptor is exposed to damping water during printing. Though in the graphic art there has recently been a need for electrophotography utilizing lithographic printing materials having such long press life as to provide not less than 10,000 sheets of copies, interlayers which have so far been proposed are not sufficiently satisfactory in adhesion between support and photoreceptive layer, and suffer from the defects that the photoreceptive layer is slightly delaminated during printing, white spots are generated in the image area, and toner adheres to the non-image areas to cause fog, thereby, stains by printing are generated.